Phylogeography and evolutionary history of whiting (Merlangius merlangus) and picarel (Spicara spp.) along the Turkish coastal waters

Abstract

In this study, the effects of the Turkish Straits System (TSS) on the evolutionary history and phylogeography of Spicara flexuosa and Spicara maena, and Merlangius merlangus were investigated. The results of the study indicated that the distinction of the three taxa under Spicara is possible with three different mtDNA markers, e.g. (16S, CO1, cyt-b). S. maena and S. flexuosa were also analyzed using a partial fragment of the nuclear IRBP gene. Molecular results showed that Spicara flexuosa was significantly more common in the Turkish coastal waters, when compared to S. maena. Morphological measurements revealed that the S. maena samples were smaller than the S. flexuosa samples. An absence of genetic structure between subpopulations from Turkey indicate the connectivity of the Spicara flexuosa populations, suggesting that the TSS is a corridor for gene flow for this species. Considering Merlangius merlangus, the mitochondrial DNA (CO1, cyt-b) genes and nuclear DNA (RAG1) gene were used. The results confirmed the existence of two subspecies in the sampling sites used in this study, based on mitochondrial DNA results, one in Turkish coastal waters and Greece (M. m. euxinus), and the other (M. m. merlangus) in Atlantic. High levels of genetic differentiation was observed along the Turkish coastal waters based on the cyt-b gene, suggesting that TSS potentially represents a barrier to dispersal for this species. As the whiting populations in the Black Sea were found to belong to different stocks when compared to those in the Aegean, separate conservation strategies are necessary for their protection.